Method for production of sodium bicarbonate, sodium carbonate and ammonium sulfate from sodium sulfate

Abstract

There is disclosed a process for recovering sodium bicarbonate and forming ammonium sulfate from a source containing sodium sulfate. The method involves contacting the sodium sulfate in solution with carbon dioxide and a compound containing ammonia. Sodium bicarbonate is precipitated in high purity form from the solution. It is important to maintain the temperature of the source solution at or above 32° C. This provision eliminates contamination of hydrates or ammonium bicarbonate components. The filtrate of the sodium bicarbonate reaction can be further processed to yield an ammonium sulfate product in the concentrated liquid or precipitated form in high purity. The basic process can be expanded to be combined with a conventional Claus process for sulfur recovery as a Tail Gas Unit, or can be further employed in a wet and dry scrubbing process for FGD schemes.

We claim: 
     
       1. A method of scrubbing sulfur compounds from gas containing sulfur oxide compounds and recovering inorganic values, comprising the steps of: a. providing a sodium sulfate solution;   b. contacting said solution with carbon dioxide and ammonia or ammonium ions while maintaining a solution temperature of at least 32° C. to form a precipitate of sodium bicarbonate;   c. recovering as a product said precipitate of sodium bicarbonate in step b.;   d. filtering precipitated sodium bicarbonate;   e. treating the remaining solution of step c. with sufficient ammonia of ammonium ions to form a saturated solution of ammonium sulfate and a precipitate of sodium sulfate from said solution;   f. recovering as a product said precipitate of sodium sulfate;   g. recovering ammonium sulfate as a product from the remaining solution from step e.;   h. rehydrating said precipitate of sodium bicarbonate to form a concentrated sodium bicarbonate solution; and   i. introducing said sodium bicarbonate solution into a conditioning vessel for the removal of a sulfur oxide compound.   
     
     
       2. The method as set forth in claim 1, wherein said method further includes the steps of: washing residual sodium sulfate out of said precipitate of sodium bicarbonate; and   dehydrating said precipitate of sodium bicarbonate.   
     
     
       3. The method as set forth in claim 2, wherein said step of dehydrating said sodium bicarbonate comprises dehydrating said sodium bicarbonate precipitate to less than about 10% by weight liquid. 
     
     
       4. The method as set forth in claim 1, wherein said gas is flue gas. 
     
     
       5. The method as set forth in claim 4, further including the step of removing flyash from said flue gas. 
     
     
       6. The method as set forth in claim 5, further including the step of removing flyash with an electrostatic precipitator or a baghouse. 
     
     
       7. A method of scrubbing sulfur compounds from gas containing sulfur oxide compounds in a conditioning vessel, comprising the steps of: a. providing a sodium sulfate solution;   b. contacting said solution with carbon dioxide and ammonia or ammonium ions while maintaining a solution temperature of at least 32° C. to form a precipitate of sodium bicarbonate;   c. recovering as a product said precipitate of sodium bicarbonate in step b.;   d. filtering precipitated sodium bicarbonate;   e. treating the remaining solution of step c. with sufficient ammonia or ammonium ions to form a saturated solution of ammonium sulfate and a precipitated sodium sulfate from said solution;   f. washing residual sodium sulfate out of said precipitate of sodium bicarbonate;   g. dehydrating said precipitate of sodium bicarbonate; and   h. introducing dry sodium bicarbonate into said conditioning vessel for the removal of a sulfur oxide compound.   
     
     
       8. The method as set forth in claim 7, further including the step of collecting dry sodium sulfate for introduction into said sodium sulfate solution in step a. 
     
     
       9. The method as set forth in claim 7, further including the step of recycling said carbon dioxide. 
     
     
       10. The method as set forth in claim 7, further including the step of thickening and clarifying said sodium sulfate prior to step b. 
     
     
       11. The method as set forth in claim 10, wherein said step of dehydrating said sodium bicarbonate comprises dehydrating said precipitated sodium bicarbonate to less than about 10% by weight liquid. 
     
     
       12. The method as set forth in claim 7, wherein said gas is flue gas. 
     
     
       13. A method of scrubbing sulfur compounds from gas containing sulfur oxide compounds, comprising the steps of: a. providing a source of sodium sulfate solution;   b. contacting said source of sodium sulfate with carbon dioxide and ammonia or ammonium ions while maintaining a solution temperature of at least 32° C. to form a precipitate of sodium bicarbonate;   c. recovering as a product said precipitate of sodium bicarbonate in step b.;   d. filtering precipitated sodium bicarbonate;   i. converting said precipitate of sodium bicarbonate into a sodium carbonate precipitate; and   j. introducing dry sodium carbonate into a conditioning vessel for removal of a sulfur oxide compound.   
     
     
       14. The method as set forth in claim 13, further including the step of recycling carbon dioxide. 
     
     
       15. The method as set forth in claim 13, wherein said step of converting said sodium bicarbonate to sodium carbonate comprises calcining said sodium bicarbonate precipitate. 
     
     
       16. The method as set forth in claim 13, wherein said step of converting said sodium bicarbonate to sodium carbonate comprises elevating the temperature of the sodium bicarbonate precipitate in solution. 
     
     
       17. The method as set forth in claim 13, further including the step of filtering thickening and clarifying said sodium sulfate prior to step b. 
     
     
       18. The method as set forth in claim 17, further including the step of filtering said precipitated sodium carbonate prior to step i. 
     
     
       19. The method as set forth in claim 13, wherein said gas comprises flue gas. 
     
     
       20. The method as set forth in claim 19, further including the step of removing fly ash from said flue gas. 
     
     
       21. The method as set forth in claim 20, further including the step of removing fly ash with an electrostatic precipitator or baghouse. 
     
     
       22. A method of scrubbing sulfur compounds from gas containing sulfur oxide compounds, comprising the steps of: a. providing a source of sodium sulfate solution;   b. contacting said source of sodium sulfate with carbon dioxide and ammonia or ammonium ions while maintaining a solution temperature of at least 32° C. TO form a precipiate of sodium bicarbonate;   c. recovering as a product said precipitate of sodium bicarbonate in step b.;   d. filtering precipitated sodium bicarbonate;   e. treating the remaining solution of step c. with sufficient ammonia or ammonium ions to form a saturated solution of ammonium sulfate and a precipitate of sodium sulfate from said solution;   f. recovering as a product said precipitate of sodium sulfate;   g. recovering ammonium sulfate as a product from the remaining solution of step f.;   h. washing residual sodium sulfate out of said sodium bicarbonate precipitate;   i. converting said precipitate of sodium bicarbonate into a sodium carbonate precipitate; and   j. introducing dry sodium carbonate into a conditioning vessel for removal of a sulfur oxide compound.